There is a clear plastic cover over the pit which was installed and sealed by the company that put in my radon system. When the pump ejects water to the sewer it always makes the sink upstairs gurgle.

When I say I am going to tie into the galvanized pipe, I mean as a vent only, and not as a means to drain wastewater. I would bring a new pipe out vertically and connect it into the galvanized pipe with a wye.

attach a 1.5" vent to the plastic lid and tie it into the galv. pipe at the ceiling.
Does the sink that gurgles have a vent?